1. Field of Invention
This invention relates to an insulation cover and, in particular, to an insulation cover for a elbow joint of tubular conduits.
2. Brief Statement of the Prior Art
Insulation of tubular conduits is practiced by overlaying the surface of the conduits with a porous insulating material and restraining the material by enveloping it in a flexible sheet cover. Various approaches have been used to cover the insulation at the ubiquitous right angle elbows. One of the most recent approaches uses one-piece foldable elbow covers such as disclosed in U.S. Pat. No. 3,495,629. A practical difficulty experienced with elbow covers of this patent design was that these covers were unstable in the closed or elbow-shaped configuration and required that the applicator manually restrain the cover in its closed position while applying fastening means such as staples, tape, and the like to permanently restrain the elbow cover.
An improvement in the one-piece foldable elbow cover is that disclosed in U.S. Pat. No. 3,960,181 in which it is disclosed that the elbow cover can be stabilized in its final, elbow-shape and can be provided with a pair of laterally projecting ears that are foldable between the open and closed, stable configurations. The bistable character to this elbow cover is achieved by upsetting the flexing surfaces of the elbow cover with a pair of dimples or arcuate protrusions that snap over center as the ears are flexed between their bistable open and closed positions.
The bistable character of the elbow cover was a significant improvement in the art since it provided an elbow cover stable in an open or stacking configuration, suitable for storage and shipment and stable in the closed, final elbow shape so as to permit facile installation. The elbow cover of this patent design, nevertheless required the applicator to use both hands to reverse the laterally projecting ears and the arcuate protrusions or dimples can be cosmetically objectionable.
A recently issued patent, U.S. Pat. No. 4,139,026, also discloses a one-piece, foldable elbow cover which is stable in the open, stacking configuration and the closed, elbow configuration. This patent discloses that the surface arcuate protrusions can be smoothly blended into the surrounding surface of the cover and teaches that if the depths of these protrusions, as measured from an arcuate curve of the outside radius of the tubular section, is from 3% to 10% of such radius, then the cover is also stable in intermediate, partially open positions. The difficulty with this patent design is the stability of the intermediate configurations, i.e., the partially open configurations. This requires the two-handed application of the elbow cover to a right angle insulated joint. Frequently, such joints are encountered in locations having limited access where using both hands is extremely difficult. Also, the covers of this patented design can be applied to oversized diameter lines only with difficulty since the partial spreading of the cover sufficiently to envelope an oversized line can cause the cover to flip to its stable, partially open configuration and the cover must then be manually restrained while applying a permanent retention means such as tape or staples.